1. Field of the Invention
The present invention relates to communications; more specifically, communications in a multi-service provider environment.
2. Description of the Related Art
FIG. 1 illustrates a portion of the radio frequency spectrum. Frequency range 210 centered around 800 MHz has historically been known as the cellular frequency range and frequency range 212 centered about 1900 MHz is a newer defined frequency range associated with personal communication services (PCS). Each range of frequencies, i.e., the cellular and PCS, are broken into two portions. In cellular frequency range 210, there is uplink portion 14 which is used for communications from a mobile communication device to a base station such as a cellular base station. Portion 216 of cellular frequency range 210 is used for downlink communications, that is, communications from a cellular base station to a mobile communication device. In a similar fashion, Portion 218 of PCS frequency range 212 is used for uplink communications, that is, communications from a mobile communication device to a base station. Portion 220 of PCS frequency range 212 is used for downlink communications, i.e., communications from a base station to a mobile communication device.
Each of the frequency ranges are broken into bands which are typically associated with different service providers. In the case of cellular frequency range 210, frequency bands 230 and 232 are designated band "a" for uplink and downlink communications, respectively. In a particular geographic area, a cellular service provider is assigned frequency band "a" in order to carry out mobile communications. Likewise, in the same geographic area another cellular service provider is assigned frequency bands 234 (uplink) and 236 (downlink) which are designated band "b". The frequency spectrums assigned to the service providers are separated so as to not interfere with each other's communications and thereby enable two separate service providers to provide service in the same geographic area. Recently, the US Government auctioned the PCS frequency spectrum to service providers. As with the cellular frequency range, the PCS frequency range is broken into several bands where a different service provider may use a particular frequency band for which it is licensed within a particular geographical area. The PCS bands are referred to as A, B, C, D, E and F. The A band includes uplink band 250 and downlink band 252. The B band includes uplink band 254 and downlink band 256. Band C includes uplink band 258 and downlink band 260. Each uplink and downlink band of the A, B and C bands are approximately 30 MHz wide. The D band includes uplink band 262 and downlink band 264. The E band includes uplink band 266 and downlink band 268. Likewise, band F includes uplink band 270 and downlink band 272. The uplink and downlink bands of bands D, E and F are approximately 10 MHz wide each. It should be noted that with the cellular and PCS frequency bands, it is possible to have as many as eight different wireless communication service providers in a particular area.
Each of the different cellular and PCS bands consist of control channels and communication channels in both the uplink and downlink direction. In the case of analog cellular bands, there are 21 control channels for both the "a" and "b" bands. Each of the control channels include an uplink and a downlink portion. The control channels transmit information such as an SOC (System Operator Code), an SID (System Identifier Code), paging information call setup information and other overhead information such as information relating to registering with the mobile communication system. The portion of the cellular band's spectrum not occupied by the control channels is used for communication channels. Communication channels carry voice or data communications, where each channel consists of an uplink and downlink communications link. Presently there are several cellular communication standards. An analog standard known as EIA/TIA 553 was built upon the AMPS (Advanced Mobile Phone Service) standard. This standard supports 21 analog control channels (ACC) and several hundred analog voice or traffic channels (AVC). A newer standard is the EIA/TIA IS54B standard which supports dual mode operation. Dual mode operation refers to having an analog control channel, and either an analog voice/traffic channel or a digital traffic channel (DTC). The AVC or DTC are used for actual communications, and the ACC is used to transfer information relating to, for example, call set-ups, service provider identification, and the other overhead or system information.
A newer standard, the EIA/TIA IS136 standard supports communications covered by both analog and dual mode cellular, and also includes a totally digital communication scheme which was designed for the PCS frequency bands A-F and cellular frequency bands "a" and "b". This standard allows for a digital traffic channel (DTC) and a digital control channel (DCCH). In the case of the DTC, not only is the voice or data communicated, but in addition, a digital channel locator (DL) is transmitted in the DTC. The DL enables a mobile communication device that locks onto the DTC to use the information in the DL to locate a DCCH for purposes of obtaining information such as the SOC, SID, paging information, and other system overhead information carried on the digital control channel.
When a mobile communication device such as a mobile telephone attempts to register with the service provider, it locks onto a control channel and reads information such as the SOC and SID. If the SOC and/or SID correspond to a service provider with which the user has a communication services agreement, the telephone may register with the service provider's mobile communication system via the up-link control channel.
FIG. 2 illustrates a map of the United States illustrating cities such as Seattle, Chicago and Washington, DC. For example, in Seattle frequency band A has been licensed to SOC (Service Operator Code) 001 with a SID of 43 and band C has been licensed to SOC 003 with a SID of 37. In Chicago, suppose that frequency band C has been licensed to SOC 001 with a SID equal to 57, and that band B has been licensed to SOC 003 with a SID of 51. In Washington, DC suppose that frequency band "a" has been licensed to a SOC 001 with a SID of 21, and that band A has been licensed to SOC 003 with a SID of 17. It should be noted that the same SOC may be found in several different locations although on different frequency bands. It should also be noted that the same SOC will be associated with different SIDs in each geographical area and that in the same geographic area different service providers have different SIDs. If a particular subscriber to a wireless telecommunication service has an agreement with a service provider having a SOC of 001, that subscriber would prefer to use systems with a SOC of 001 because the subscriber is likely to receive a less expensive rate. When the subscriber is in Seattle he/she would prefer to be on band A, and if in Chicago on band C, and if in Washington, DC on band "a". The above described situation presents a problem for a wireless communication service subscriber. As a subscriber moves from one area of the country to another, the telephone when turned on, searches for the "home" service provider, or the service provider with which the subscriber has a pre-arranged agreement. If for example, the subscriber travels from Seattle to Chicago, when turning the phone on in Chicago, the phone will search through the different bands of the spectrum to identify the service operator with the code 001 in order to find the desired service provider.
In order to find a particular service provider, the phone may have to search through both the "a" and "b" cellular bands, and through the eight PCS bands. It should be recalled that there are up to 21 different ACCs in each of the "a" and "b" cellular bands. It may be necessary to check 42 ACCS in order to find an ACC from which a SOC or SID may be obtained. Additionally, searching for a particular SOC or SID in PCS bands A through F is particularly time consuming. The digital control channels (DCCHs), which contain the SOC and SID, are not assigned to specific frequencies within a particular PCS band. As a result, the mobile communication device may find it necessary to search through the spectrum of each PCS band looking for a DCCH, or an active DTC that has a digital channel locator (DL) which will direct the mobile communication device to the DCCH. As illustrated above, the process of searching for a particular service provider is laborious and may require a period of time on the order of several minutes.
This problem has been addressed by storing a search list in the phone. The list typically starts with an optimal service provider and its frequency band followed by preferred service providers and each of their associated frequency bands. The list is ordered such that more preferred service providers precede less preferred service providers. The list may also contain service providers that are only used for emergency calls. The service providers are identified by their SOCs and/or SIDs. As a result, the phone attempts to locate and register with the optimal or more preferred service providers before attempting to obtain service from a less desirable service provider. This technique reduced the amount of time required for a phone to locate a desirable service provider; however, it did not provide a list that was optimized for different geographic locations.
As a result of this drawback, lists based on geographic location have been created. This technique involves storing a larger list in the phone. This larger list is broken into sublists where each sublist is associated with a different geographic area. The sublists are delimited by a single bit that indicates the first entry of a new sublist. When a phone attempts to register with a service provider, the phone checks the entire list for a SID that matches the SID being received. Once a match is located, the phone goes to the top of the sublist in which the SID is located by locating the delimiter bit. The optimal service provider's SID and/or SOC and frequency band are then obtained from the top of the sublist, and are used to attempt to locate and register with the service provider. If the phone is unsuccessful, the information relating to the next most preferred service provider is obtained and the phone attempts to locate and register with that service provider. This process continues until the phone successfully registers with a service provider. Over time, relationships between service providers change and therefore the sublist associated with a particular geographic area may change. These changes may be entered using the keyboard or over the air programming. Unfortunately, in order to change one sublist, the entire collection of sublists must be reprogrammed into the phone's memory. This is a time consuming and error prone process because of the large amount of data being transferred.